I know this is off-topic, but could someone explain to me the progression of smaller thread sizes, that is, sizes smaller than 2-56? In metric I'm familiar with M2 and M1.7 but that's about it.

On topic I'll just add a reminder that the Pup didn't actually use turnbuckles so I'd be hesitant to fork over the cash for a set of Proctor turnbuckle, which aren't even particularly scale in appearance when you look at actual WWI turnbuckles. I when the music wire route on my Snipe, but I can understand how some people might be hesitant to do this. Who knows what I'll end up with. But if I do go the route of using cable instead, I don't think I'd mess around trying to make them adjustable on a 1:6 scale model.